Investigate if role impersonation works in integration tests

[pmalek]

Problem statement

gateway-operator/test/integration/suite.go

Lines 227 to 234 in c1fdd11

	cfg.NewClientFunc = func(config *rest.Config, options client.Options) (client.Client, error) {
	// always hijack and impersonate the system service account here so that the manager
	// is testing the RBAC permissions we provide under config/rbac/. This helps alert us
	// if we break our RBAC configs as the manager will emit permissions errors.
	config.Impersonate.UserName = "system:serviceaccount:kong-system:controller-manager"
	return client.New(config, options)
	}

sets the role to impersonate in integration tests to test RBAC policy rules that is used for the manager.

Recently there's been several issues that slipped through the tests and surfaced in charts (e.g. Kong/charts#1146 and Kong/charts#1137 (comment))

This issue tracks to effort to verify why impersonation didn't work for these problems.

Acceptance criteria

• As KGO developer I know that manager's policy rules are tested and I am sure that my changes are not going to accidentally cause RBAC errors for end users without causing tests failures.